Hydrodynamic cavitation reactors are devices for intense generation of cavitational events for fluid processing. These devices mostly are without any moving elements. Examples of these devices include, but are not limited to an orifice, venture, vortex diode, etc. More particularly, vortex diodes are among most useful fluidic devices, which do not have any moving elements. The basic design of a vortex diode consists of a disc-shaped chamber with a cylindrical axial port and at least one tangential port. Such devices have been modified over the years by many researchers and designers to improve their function as well as to use them for purposes other than as valves.
Effluents from various industries, such as chemical, distilleries, fisheries, and the like, have the issue of high ammoniacal nitrogen content in their wastewaters while the limit set by pollution control boards usually is around 50 mg/l for industrial wastewaters. Ammoniacal nitrogen commonly represents the amount of nitrogen compounds or pollutants, as ammonia in water. This is an important parameter in water analysis, especially, for wastewater treatment to protect environment.
Several chemical methods are known in the art for treating effluent to control ammoniacal nitrogen. Example of such chemical methods include, but are not limited to the biological methods of treatment and other physico-chemical methods, such as ion exchange, charge neutralizing species or coagulants. A few physical methods also exist for the treatment of wastewater, such as filtration, electro-oxidation, electro-coagulation, froth floatation, adsorption, etc. There are certain nitrogen containing organic pollutants, especially in wastewaters from industries such as dyes, pigments, colourants, distillery, etc. These nitrogen containing organic pollutants are considered refractory compounds, which are difficult to remove or degrade by using conventional methods of chemical or biological treatment. For such pollutants, newer techniques have to be explored, where extreme conditions can break down pollutants and nitrogen containing organic molecules.
Most of the existing wastewater treatment methodologies differ significantly from each other not just in their principles, but also in the form of application, process economics. Further, it has huge differences in land, equipment, and material requirements. Further, since effluent treatment is more complicated due to varied types of pollutants including organic and inorganic pollutants, new strategy is required involving novel materials, methods, and process integration options and technology for wastewater treatment.
Cavitation technology in recent years is found to be substantially beneficial in waste water treatment. Cavitation is a phenomenon of formation, growth, and collapse of micro bubbles within a fluid. Cavitation occurs due to increase in kinetic energy of the fluid at the expense of local pressure when the fluid passes through constriction. Hydrodynamic cavitation known in the art utilizes constriction such as orifice or venturi in the path of flow of fluid. Moreover, cavitation is realized due to linear velocity of fluid in conventional devices. Vortex diode disclosed in this invention on the other hand uses rotational flow to generate cavitation. The nature of cavities, more particularly, number density of generated cavities and intensity of collapse of generated cavities, in such rotational flows realized in vortex diode is significantly different than the other hydrodynamic cavitation devices known in the art as orifice or venturi, which are based on the constriction of flow.
Vortex diodes, which use cavitation and collapse of cavities generated due to rotational flows, have been hitherto unexplored for the treatment of effluents, more particularly, the effluents generated from highly polluting industries, such as distilleries, dye, pigments, and other colour effluent generating industries. The effluents generated from such highly polluting industries have high COD, ammoniacal nitrogen or colour have not been subjected to cavitation treatment for removal of ammoniacal nitrogen using process intensification by various types of cavitation devices.
Vortex diodes employ fluid vortex phenomena for its operation. The basic design of a vortex diode consists of a cylindrical axial port, a tangential port, and a chamber connecting the two ports. The chamber is characterized by its diameter and height, which decide the chamber volume. The flow entering the vortex diode through the tangential port sets up a vortex, and establishes a large pressure drop across the vortex diode.
U.S. Pat. No. 4,112,977 discloses a vortex diode wherein the tangential ports can be formed as push-fit into the main body of the vortex diode. It is recommended to have as many tangential ports as possible to improve flow symmetry and reduce pressure losses.
U.S. Pat. No. 6,358,415 discloses a sewage disposal apparatus, more particularly, a vortex sewage disposal apparatus for the disposal of sewage at construction sites.
The effective reduction in ammoniacal nitrogen from wastewaters is a serious challenge for existing treatment technologies. Therefore, there is need to develop an effective process for the reduction of nitrogen from effluents. The process intensification of this invention has not been reported earlier for reduction in ammoniacal nitrogen, especially, for all types of cavitation reactors.